Enterobacter spp. are Gram-negative, rod-shaped, motile, nonsporeforming bacteria having nonmotile exceptions such as E. asburiae, E. dissolvens, E. nimipressuralis and E. hormaechei. Some of the species, such as E. sakazakii have been found in powdered milk products and have been associated with high infant fatality rates. Enterobacter, particularly Enterobacter cloacae and Enterobacter aerogenes, are important nosocomial pathogens responsible for a variety of infections, including bacteremia, lower respiratory tract infections, skin and soft tissue infections, urinary tract infections (UTIs), endocarditis, intra-abdominal infections, septic arthritis, osteomyelitis, and ophthalmic infections. Among the predisposing factors for such bacterial infections by humans are prolonged hospitalization, in particular in an intensive care unit (ICU); prior treatment with antibiotics; general debilitation; and immunosuppression.
The treatment of Enterobacter is complicated by the fact that multiple strains have antibiotic resistances. These bacteria possess inducible beta-lactamases, which are undetectable in vitro but are also responsible for resistance during treatment. Physicians treating patients infected with these bacteria are well advised to avoid certain antibiotics, such as third-generation cephalosporins, because resistant mutants can quickly appear. The crucial first step of treating an infected patient is appropriate identification of the bacteria. However, problems associated with identification occur. The clinical presentation of the various Enterobacter infections is not specific enough to permit clinical differentiation from that of other bacterial infections, such as Klebsiella and Citrobacter. Such Enterobacter identification is further complicated by the fact that strains of the Enterobacter species are genetically and phenotypically heterogeneous making it difficult to develop a test that would identify all strains.